The exemplary embodiments of the present invention relates to a method and a device for stabilizing a cavity excavated in underground construction. This method and this device are preferably applied in poor rock which exerts pressure but has little strength.
In underground structures (tunnels, galleries, caverns, and the like), a known procedure is to secure the excavated cavity using a lining, i.e., using supporting means such as steel arches, gunned concrete, anchors, and prefabricated concrete elements (tubing). In poor pressure-exerting rock of low strength, the profile of the excavated cavity has a tendency to narrow. This results in forces acting on the lining which generate compressive stresses in the supporting means. The known supporting means under these circumstances are therefore designed so a to be able to give way. As a result of this giving-way action, the pressure of the rock generally subsides.
Publication EP-B-1 034 096 is the most obvious prior art here which shows and describes a tunnel lining which has at least two lining elements acting as supporting segments which are separated by a contraction joint running longitudinally within the tunnel. Upset tubes have been placed into these contraction joints, each of which is located between an outer and inner upset tube and mounted at their faces between two pressure-transfer plates. Pressure is transferred through these pressure plates from the lining segments onto each upset tube. At a given axial load exceeding the buckling resistance of the upset tube, the upset tube buckles in stages and becomes shorter. While overcoming a resistance in the circumferential direction of the tunnel, the lining segments are able to move towards each other and simultaneously exert a resistance of the structure against the rock.
This known tunnel lining has certain practical disadvantages. In the area of the faces of the upset tubes, a local concentration of stress occurs in the lining segments. As a result, other measures must be taken beyond the installation of the pressure transfer plates in order to preclude the lining segments from sustaining damage due to this concentration of stress. This action is disadvantageous in terms of cost. In the case of a lining composed of gunned concrete, the contraction joint must additionally be protected during production of the lining against penetration by the gunned concrete. In addition, problems may arise from a possible tilted position of the upset tubes due to transverse movements by the lining segments relative to each other.